DEAD Sony TV

I have 27 inches Sony TV, model KV-27S15. The TV set went dead after I heard a pop sound . Open the back of the TV and visual inspect I found the body of resistor R607 (0.1 OHM, 1/2 Watt) was burned. Inspect the main fuse, it is good. After troubleshooting and repalcing all components listed below I restored the normal operation to the TV.

Q601 = 2SC4834 (Switching power transistor) Q602 = 2SC4834 (Switching power transistor) Q591= 2SC4927 (TV Horizontal defection output) R607= 0.1 OHM, 1/2 Watt

But the TV works as normal for only 15 minutes then I heard the pop sound again and the TV went DEAD. I replaced four components above again and the TV now only runs as normal for 10 minutes and I heard the pop sound the TV now is DEAD.

I need some help to find the cause of this problem.

Reply to
TS
Loading thread data ...

yes replace ic 600 , with all the other componats you replaced that ic is a rugulator usually it blow a hole in itself and lets the smoke out, when you let all the smoke out the ic will not work HA HA

Reply to
David Naylor

If that IC were damaged wouldn't the set not work at all?

I've heard of some Sony sets with similar symtoms that were very picky about the parts you use. Try ordering the components straight from Sony, also monitor the temperature in operation, if the HOT is getting more than warm to the touch something is still wrong.

Reply to
James Sweet

Art is dead on here. These are very routine repairs, usually caused by bad solder joints on the H-drive transformer, cusing the HOT to short, taking out the PS regulators. Replace the parts listed, look over the caps related to the two PS transistors for cracks very carefully, and make sure you get good quality parts from a reputable vendor. Use only P rank 2SC4834 transistors. You can get them from TriTronics, B&D or Acme. If anyone tells you that you need to buy the parts from Sony, don't bother, as long as you use one of the quality suppliers listed above. We replace the HOT with a 2SD1881 because extensive testing showed that it runs cooler and quieter than the original and have had a perfect reliability record for us. Just be sure to go through the drive circuit carefully as Art suggested. We match the power supply transistors for gain and junction bias voltages because we buy them in quantities, but this is not realy necessary if you get the P rank transistors. Actually the N rank or better will be fine in most cases.

There have been a few cases of sets with bad flybacks that can eat these parts repeatedly, but they are relatively rare. We have repaired this scenario many time as described.

Some techs will tell you to routinely change the VDRs as well. They should be checked for shorts, but when the failure is due to HOT shorting, the VDRs are always fine. In cases where the PS fails on its own or due to external causes, the VDRs are always suspect, as are the caps on the switching transistors in the PS and the convertor.

It is a good idea to brign the PS up slowly on a variac and watch the switching for 50% duty cycle and better than 50kHz operation as it begins to run. If these two conditions are not met there is more troubleshooting to do and the PS will likely blow if powered up fully.

Leonard

-------------------------------------------------------------------------------- I am using the free version of SPAMfighter for private users. It has removed 14519 spam emails to date. Paying users do not have this message in their emails. Try SPAMfighter for free now!

Reply to
Leonard Caillouet

Thanks for the tips. I will let you know if I find something.

Reply to
TS

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.